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Textbook question - piercing valves

Hello all,

I've been looking through my HVAC textbook between semesters and read that piercing valves should be removed once system access is no longer needed. This of course goes for the non-permanent type but my question is, how on earth do you remove a piercing valve and not lose your refrigerant? What am I missing here that the textbook does not cover?

I'm now thinking that what they failed to mention is that a tech can use a piercing valve to access the system in order to evacuate, install permanent service valves and make any necessary repairs before charging.

Lol...true. I was given a 2 ton window unit that the previous ho put a screw through the coil. BRand new otherwise but I would like to attempt a fix and install in my shed.

Ok I can see your point there. I would get the taps that you braze in, pierce, then do what you need to do and leave it in there. All the other ones are prone to leak. If you really want an adventure then try doing all your work from the process tube off of the compressor!